1. Field of the Invention
The present invention is related to three-dimensional measurement of an object with varying dimensions in all three directions and, more particularly, to a system for measuring stator half coils and full coils.
2. Description of the Related Art
Electrical generators used to produced electricity in power plants have stator coils formed, by two "half coils". Each half coil may be as 36 feet in a large generator. The stator half coils typically have a rectangular cross-section and are formed of stacks of thin metal strips covered with insulation surrounded by tape spirally wound on the coil. The central section of a stator half coil comprises the majority of its length and is straight. However, the end sections of a stator half coil form a complex curve, part of which is shaped like an involute on the inside of a cone. An example of the end section 10 of a conventional stator half coil 11 is illustrated in FIG. 1. As indicated at 12, the stator coil has a rectangular cross-section and the complex curvature of the stator coil end 10 can be seen in the perspective view of FIG. 1.
It is important to manufacture stator half coils so that their actual or measured shape matches the designed shape within relatively close tolerances. The ends 14 of the straight section 16 should align within 0.04 cm (0.15 inch) and the tips 18 of the curved section should be within 0.95 cm (0.375 inch), so that the generator can be assembled with proper clearances and the half coils can be connected to form full coils. However, due to considerable variance in the length, thickness and the shape of the curved end sections 10 of stator half coils, precise measurement of the end sections 10 is difficult and time consuming. Therefore, the position of the tip 18 relative to the end 14 of the straight section 16 is all that is conventionally measured. This makes connectability of half coils to form a full coil reasonably certain; however, the curvature of the end section 10 remains unknown. If the curvature is incorrect, the proper clearances will not be provided. This could result in preventing connection of the half coils until the end section 10 is reformed after installation of the half coils into a partially constructed generator has already begun. Such trial and error construction of stator coils is highly undesirable.